Transportation of vaccines is a critical component for improving vaccination rates in low-income countries and warrants more attention, according to a computer simulation by the HERMES Logistics Modeling Team at the University of Pittsburgh and Pittsburgh Supercomputing Center (PSC). The team recently reported their findings in the PLOS ONE online journal (http://dx.plos.org/10.1371/journal.pone.0064303).

Each year, millions of dollars of potentially lifesaving vaccines fail to reach populations throughout the world. Most aid programs tend to focus more on purchasing vaccines or donating refrigerators and freezers to help ensure vaccine delivery. The computer simulation of the West African nation of Niger showed that improving transportation as well could improve vaccine availability among children and mothers from roughly 50 percent to more than 90 percent.

Above: Each line depicts a different vaccine transport route in Niger, with the line colors representing how much of the available transport capacity in each route is being used (the more red the line, the more the vehicle or carrier is being filled or overfilled).

“The vaccine supply chain is a complex orchestra of people, facilities, equipment, vehicles, vaccines, and other products that needs to be coordinated to get vaccines from manufacturers to people,” says Bruce Y. Lee, MD, MBA, corresponding author, associate professor of medicine and biomedical informatics at the University of Pittsburgh. Lee is scientific lead for the Logistics Modeling Team developing HERMES (Highly Extensible Resource for Modeling Supply Chains), which allows users rapidly to create a simulation model of any vaccine distribution system or supply chain. Like a “SimSupply Chain,” HERMES includes virtual representations of every component and process in a country’s vaccine supply chain, including virtual trucks, motorbikes and people.

“For many decades, coordinating the vaccine supply chain has been a challenge anywhere, and a particular challenge in lower-income countries,” Lee says. “Our team’s goal is to provide state-of-the art computer solutions to tackle this longstanding problem.” The team works closely with a number of international organizations, including national Ministries of Health, UNICEF, the World Health Organization (WHO), Agence De Medecine Preventive (AMP), PATH, Village Reach and the Clinton Health Access Initiative (CHAI).

Seemingly small changes in vaccine supply chains can have ripple effects throughout the system, and in turn impact thousands and even millions of lives.

“As in air traffic control, freight delivery or any other complex transport system, it’s difficult for a person or group of people to figure out what is happening without the benefit of computer simulation,” says Shawn Brown, PhD, coauthor, director of public health applications at PSC and technical lead of the Logistics Modeling Team. “Thanks to the simulation, it became clear that transport was a critical factor for vaccine delivery.” The fifteen-person HERMES team includes experts from a range of disciplines, including Joel Welling, PhD, senior scientific specialist at PSC, and Leila Haidari, MPH, a senior analyst on the team and first author of the report.

Prior to the development and use of HERMES, testing changes in vaccine supply chains often involved trial and error — a very costly approach. Many previous analyses focused on the known problem of stationary storage devices like refrigerators and freezers. Because of this body of work, aid groups like UNICEF did as well.

“One of the critical things HERMES is great at is the role of transportation in the supply chain,” Brown says. “It’s a lot easier to buy a bunch of refrigerators and send them to a country … but understanding the dynamics of the transport system without the help of a simulation model isn’t a trivial matter at all.”

Simulating the Niger supply chain for a year allowed the HERMES Logistics Team to explore the impact of different changes. Adding an unlimited number of refrigerators and freezers for vaccine storage at national, regional and local facilities increased the fraction of kids vaccinated by 11 percent. On the other hand, doubling the number of vehicles or the frequency at which they traveled increased vaccination by 26 percent. Tripling transport increased it by 30 percent. In fact, improving transport decreased the need for storage because vaccine doses didn’t have to wait as long at each storage location before moving down the supply chain.

Importantly, improving transportation may come at a lower price tag than purchasing more refrigerators or freezers. Improving transportation does not necessarily mean buying more vehicles. Instead, it may involve potentially less expensive upgrades such as providing fuel, re-allocating vehicles to different purposes or locations, making sure vehicles are available at the right times, paying drivers more or changing the routes that vehicles travel. The specific solution may be different for different locations.

“Many countries rely on trucks that are often not available because they are being used for other purposes, or employ vehicles that are poorly serviced, riding animals or walking by foot” to deliver vaccines, Lee says. “Transportation is such an important part of vaccination programs, but currently a relatively small percentage of the money and attention that goes to vaccines and vaccine programs supports trucks, motorbikes, boats, their drivers and their operations.”

While some organizations concentrate on transportation, such as Transaid, Riders for Health, and VillageReach, much greater attention on this factor may be warranted, he adds. “When given a choice between fixing transport and storage, many times fixing transportation gives you more bang for the buck.”

The HERMES Logistics Modeling Team continues to collaborate with officials and other international organizations in a number of countries, including Benin, India, Senegal, Thailand and Vietnam, to build and refine simulation models of their vaccine supply chains.

About PSC: Pittsburgh Supercomputing Center (http://www.psc.edu) is a joint effort of Carnegie Mellon University and the University of Pittsburgh together with Westinghouse Electric Company. Established in 1986, PSC is supported by several federal agencies and private industry, and is a major partner in the National Science Foundation XSEDE program.

About the University of Pittsburgh School of Medicine:The University of Pittsburgh School of Medicine educates physicians who are science-based, skilled and compassionate clinicians prepared to meet the challenges of practicing medicine in the 21st century, and educates investigators who are prepared to conduct cutting-edge biomedical research focused on bettering the human condition and advancing the fundamental understanding of medical science.